Grout Injection Research Articles

Multi-resistivity survey method to confirm the quality of grouting injection

Grouting method is widely used to reinforce soft strata in reinforcement engineering projects. But few methods are available to confirm the quality of grout injection. In this manuscript, a multi-resistivity survey method is proposed to evaluate the grout reinforcement effect after grouting. Firstly, coordinate transformation equations are established, and electrical resistivity tomography (ERT), cross-hole electrical resistivity tomography (Cross-hole ERT) and principal component analysis (PCA) methods are applied to obtain a three-dimensional (3D) resistivity imaging. Then, numerical analysis with three types of synthetic grouting models is performed to study the grouting resistivity change and verify the method feasibility. Finally, a field application is conducted to show the use of the method. Results show that: 1) Grouting rises the resistivity of reinforced area. 2) Both ERT and Cross-hole ERT methods can reflect the resistivity changes, and PCA method is useful to get a more precise resistivity imaging. 3) The farther away from the grouting opening, the less grout. In the same formation, the deeper the depth, the shorter the grout diffusion distance. 4) To improve the grouting reinforcement effect, grouting boreholes should be encrypted, then their respective grouting reinforcement zones would intersect, forming a collaborative grouting reinforcement area.

A new grouting procedure to enhance axial response of helical piles in sand

Helical (or screw) piles are deep foundation elements consisting of a steel shaft with single or multiple helical plates (helices) attached near the base of the shaft. The helices and shaft are rotated into the ground using a torque motor located at the head of the shaft. The axial resistance of the piles is provided through bearing on the helices with some additional axial resistance derived from skin friction on the shaft. This paper examines the benefits of a variation of this foundation system in sandy soils, which involved post-installation injection of a cementitious grout in the vicinity of the helix. The intent is that the grout adds a bond strength to a volume of sand that has a larger diameter than that of the helix, thereby increasing the bearing resistance. A new set-up devised to facilitate easy and rapid grouting to take place is first described. The benefits of grouting are then examined in a series of full-scale static tension and compression tests performed at sand sites in Perth, Australia involving both grouted and un-grouted single helix piles. It is demonstrated that grouting led to doubling of axial stiffness and capacity with the addition of just 80 litres of grout to a 350mm diameter helix. The increases observed are quantifiable by combining a recently published design method with measured injected grout volumes.

Experimental research into the injectability of cement grouts in reef limestone

Experimental research into the injectability of cement grouts in reef limestone

Laboratory investigation of liquefaction mitigation in sand using zeolite-cement injection

The study on liquefaction mitigation using cement-based materials in soils with liquefaction potential is of great interest. As cement production is a costly and environmentally polluting process, replacing part of it with environmentally friendly and cheaper materials such as natural zeolite is very important and attractive. In the present study, to evaluate the improvement of the liquefaction resistance in loose sand using zeolite-cement injection, a series of triaxial tests was performed. Also, the liquefaction potential of injected specimens was investigated based on the results of bender element, unconfined compressive strength and monotonic triaxial tests. The results of the study indicated that the injection of tested sand with zeolite-cement grout is significantly effective in liquefaction mitigation of the sand. Even under very strong earthquakes, liquefaction did not occur in the injected specimens with water to cementitious materials' ratio (W/CM) of 3 and a cement replacement with zeolite (Z) up to 70 %. The optimum amount of zeolite (Zopt) corresponding to the maximum liquefaction resistance was 30 %. It was shown that, considering the optimization of energy consumption as well as environmental considerations, for earthquakes with a CSR ≤ 0.2, by grout injection with Z90 and W/CM of 5, the used sand liquefaction resistance is more than double. For more severe earthquakes (CSR ≤ 0.3), injection with a grout containing Z70 and W/CM of 7 resulted in no liquefaction. To counteract the liquefaction under very strong earthquakes (CSR0.5), grout injection with Z50 and W/CM of 5 can be effective.

Stabilisation of subsoil using colloidal silica beneath shallow foundation - a case study

Shallow foundations are commonly used to support various equipment in industrial projects. If the subsoil is too weak to withstand the equipment loads, the settlement or tilting of the foundations takes place. To avoid further distress to such foundations, weak soil beneath the damaged foundation is required to be strengthened. This paper presents a similar case study wherein the strengthening of subsoil was performed beneath the shallow foundations which experienced settlement and tilting beyond the permissible limits due to the presence of weak subsoil. The stabilisation of soil was performed using injection grouting with colloidal silica-based chemical grout to prevent further settlement and tilting of foundations. The particulars of the chemical stabilisation program, injection methodology, chemical consumption, field trials, and laboratory test results are explicated in this paper with the details of post rectification performance of the test foundation. The properly executed injection grouting using chemical components was observed to be an effective measure to stabilise the subsoil by enhancing its engineering properties to a certain extent. The key factors that can affect the performance of colloidal silica-based chemical and precautions to be considered during soil stabilisation are also discussed in this paper.

Subsidence Prediction Method Based on Elastic Foundation Beam and Equivalent Mining Height Theory and Its Application

Grouting technology in overburden separation is recognized as an effective method to prevent surface subsidence and reuse solid waste. This study used mechanical analysis to explore deflection characteristics of key strata and accurately predict and control surface subsidence. Conceptualizing the coal–rock mass beneath the key strata as an elastic foundation, we developed a method to calculate the elastic foundation coefficients for various regions and established an equation for key strata deflection, validated through discrete element numerical simulations. This simulation also examined subsidence behavior under different grout injection–extraction ratios. Additionally, combining the equivalent mining height theory with the probability integral method, we formulated a predictive model for surface subsidence during grouting. Applied to the 8006 working face of the Wuyang Coal Mine, this model was supported by numerical simulations and field data, which showed a maximum surface subsidence of 546 mm at a 33% injection–extraction ratio, closely matching the theoretical value of 557 mm and demonstrating a nominal error of 2%. Post-grouting, the surface tilt was reduced to below 3 mm/m, meeting regulatory standards and eliminating the need for ongoing surface structure maintenance. These results confirm the model’s effectiveness in forecasting and controlling surface subsidence with grouting. The study can provide a basis for determining the grouting injection–extraction ratios and evaluating the effectiveness of surface subsidence control in grouting into overburden separation projects.

Characterization of load-bearing and failure properties of fractured rock masses reinforced by negative pressure grouting

Grouting injection is a vital technique for addressing the challenges of high stress and significant deformation in the surrounding rock during deep mining operations, playing a crucial role in promoting green and low-carbon extraction methodologies. In this study, grouting reinforcement processes were examined by conducting grouting experiments on a fractured rock with varying negative pressures (0-100 kPa), followed by uniaxial compression testing of the grout-reinforced bodies. This investigation explored the diffusion patterns of grout under negative pressure and established a constitutive model of damage-bearing capacity for bodies reinforced by negative pressure grouting. It further studied the enhancement effect of negative pressure on the load-bearing capacity of the reinforced bodies and analyzed the instability mechanism of damage and failure in these bodies. The results indicated that the diffusion of grout under negative pressure is influenced by four types of forces, which alter the extent of grout diffusion within the fractured rock mass. Introducing a damage constitutive model that serially connects pore and framework elements characterizes the damage and failure behavior of grout-reinforced bodies under different negative pressures. As the negative pressure increases, changes in porosity, water-to-cement ratio, and admixture quantity occur in the grout-reinforced specimens, with the strength mean curve showing a trend of first increasing and then decreasing, reaching a threshold at a negative pressure of 60 kPa. With increasing negative pressure, the negative pressure damage variable decreases and then increases, and the stronger the interfacial microelement connections caused by the negative pressure, the greater the bearing capacity, ultimately manifesting in different failure modes.

Effects of superplasticizer on properties of calcined ginger nuts-based grouting material for earthen site cracks

Grout injection is an effective technique for repairing cracks in earthen sites. This study aims to address the challenges of Calcined Ginger Nuts (CGN)-based grout and enhance its engineering performance by investigating the compatibility of different superplasticizers. We examined the effects of Polycarboxylate Superplasticizer (PCE) and Naphthalene Superplasticizer (PNS) on the properties of CGN-based grout, focusing on fluidity, rheological properties, mechanical strength, volume stability, color difference, and pore structure. The engineering applicability of the optimized CGN-based grout with superplasticizers was assessed using COMSOL Multiphysics. The results show that fluidity increased with higher dosages of PCE and PNS. The grout containing these superplasticizers behaved as a shear-thinning fluid, following the power law model. Specifically, the consistency coefficient of grout with 0.5 wt% PCE and PNS decreased by 39.73% and 64.83%, respectively. Additionally, 2.9 wt% PCE and PNS reduced volume shrinkage rate by 6.86% and 6.27%, respectively. Initially, increasing the dosage of PCE and PNS improved compressive and flexural strength, but these properties later declined. XRD analysis revealed that PNS above 1.1 wt% and PCE weakened the hydration reaction, while both superplasticizers promoted carbonation. Mercury Intrusion Porosimetry (MIP) showed that 1.1 wt% PCE and PNS reduced the proportion of capillary pores by 13.79% and 10.11%, respectively. Based on these findings, 0.5 wt% PNS demonstrated the best compatibility with CGN-based grout, whereas PCE showed poor compatibility. Numerical simulations using COMSOL Multiphysics confirmed that 0.5 wt% PNS provided superior grouting effectiveness. Therefore, the CGN based grout with 0.5wt% PNS demonstrates excellent engineering performance and applicability. This study offers valuable insights into optimizing CGN-based grout for the preservation of earthen sites.

Integrating Sonic Pulse Velocity Tests with Masonry Classification for Heritage Conservation: An Insight from On-Site Diagnostic Campaigns

ABSTRACT The preservation of architectural heritage relies on a comprehensive understanding assisted by diagnostic procedures. Among non-destructive techniques, the Sonic Pulse Velocity Test (SPVT) qualifies the compactness of a masonry wall through elastic wave transmission. However, it does not directly estimate any mechanical parameters. This study presents findings from a database of 346 direct SPVTs carried out over thirteen years on both listed and ordinary buildings. Results were categorized based on masonry type according to the Italian building code, to derive information about construction quality and relate SPV with building features. Tests performed on 37 masonry panels strengthened by grout injections also confirmed the validity of SPVT in evaluating the effectiveness of the intervention. Furthermore, the Masonry Quality Index (MQI) method permitted to refine the masonry type definition through the judgment of the units’ arrangement. MQI and SPVT results were also combined by statistical analysis. These findings aim to increase comprehension of the different types of existing masonry capacity and contribute to engineering assessments for ensuring the structural safety of historical buildings.

Experimental investigation of tail void grouting pressure evolution for super-large diameter shield tunnels

The shield tunneling method is widely used in underground construction. Factors such as the variations in grouting pressure and stiffness/strength evolution over space and time directly affect ground deformation and system stability. To investigate the effect of grouting pressure variation, grouting influence zone, and hydromechanical properties on the model responses (e.g., surface settlement and lining forces), an innovative model test setup was developed to simulate the tunneling process wherein the lining could settle or float during grout injection. This setup included tunnel shrinking, loading-unloading, grout injection, and sample preparation systems. The experimental results show that the grouting pressure evolution law may be significantly affected by the tunnel translation. When the tunnel centerline was fixed in the traditional model tests, the resulting grouting pressure in the tail void was lower than that when the tunnel was free to move. This is because the tunnel translation changed the shape of the annular gap and contributed to the measured grouting pressure. The proposed setup is capable of revealing a more realistic law of grouting pressure evolution, and the subsequent spatio-temporal grouting-induced soil/lining behavior is currently being investigated.

Influence of Materials of Moulds and Geometry of Specimens on Mechanical Properties of Grouts Based on Ultrafine Hydraulic Binder.

Ultrafine hydraulic binder grout injection is a technique utilised for repairing masonry, either to connect sections, seal joints, or fill voids due to its great capacity for penetration and higher mechanical strength than lime grout. In this research, the mechanical properties of ultrafine hydraulic cement grout are analysed considering the influence of the mould material for preparing the specimens and their geometry characteristics in the context of the specifications set out in several international standards. The test campaign to ascertain compressive and flexural strength in different circumstances is supplemented with a physical and chemical characterisation of both binder and fresh and hardened grout. Significant differences in mechanical properties between specimens prepared with absorbent or non-absorbent-water material are found due to the influence of drying shrinkage and decanting binder during the curing process. Furthermore, the slenderness of specimens is presented as an important factor in determining the compressive strength of mixtures.

Evolution Mechanism and Monitoring Technology of Overburden Deformation in Underground Mining with Grout Injection

Evolution Mechanism and Monitoring Technology of Overburden Deformation in Underground Mining with Grout Injection

Isolated overburden grout injection technology mining and grouting parameters discussion and optimization

Isolated overburden grout injection technology mining and grouting parameters discussion and optimization

Investigations on the seepage characteristics of polymer grouting body for repairing HDPE geomembrane defects based on LF NMR

As high-density polyethylene (HDPE) geomembranes in landfill liner systems increasingly age and damage, seepage incidents frequently occur and severely threaten the surrounding ecological environment and groundwater safety. Targeted injection grouting with polymer materials can rapidly restore the barrier function by repairing defects in damaged geomembranes. To investigate the sealing mechanisms of polymer grouting bodies with various densities, this study used low-field nuclear magnetic resonance (LF NMR) techniques to monitor and visualize the permeation process within the grouting bodies. The results revealed two failure modes of the grouting bodies under water flows: 1) insufficient interfacial shear strength between the low-density polymer and geomembrane, leading to interfacial leakage; 2) gradual buildup of permeation pressure puncturing the foam cells of the polymer matrix and inducing permeation channels. Selecting polymers with suitable expansion ratios to produce appropriate expansive pressures is crucial to enhance interfacial shear strength while avoiding secondary damages to geomembranes. Increasing the density of the polymer grouting body can also enhance the compressive strength of foam cells and interfacial shear resistance. These are crucial for enabling grouting repair of defects in geomembranes and improving their barrier performance.

Temporal reliability evolution of a prestressed girder with post-tensioned tendons subjected to corrosion

This paper presents a methodology for the assessment of time-dependent reliability of post-tensioned (PT) girders. As possible lack of consistent maintenance efforts and the constraints of economic and temporal resources become increasingly apparent, there is a need to comprehend their remaining service life, intricately tied to the gradual evolution of their reliability over time. In this study, the primary focus is directed towards a combination of extreme load failure mechanisms and tendon corrosion. The proposed methodology is applied to a scenario involving a simply supported prestressed girder with PT tendons. The analysis takes into account the progressive reduction in bending capacity over time due to the adverse effects of tendon corrosion. Diverging from conventional approaches found in existing literature, the time-to-corrosion model embeds not only the chloride concentration in voids present in the grout injection but also considers the thermodynamic conditions necessary for the development of corrosion. A sensitivity analysis of the input variables is performed to identify the most influential parameters over time. The study shows that considering both chloride concentration and thermodynamic conditions can lead to a more realistic residual structural life. It is concluded that the consideration of the thermodynamic conditions is essential to avoid overly conservative safety assessments, which could lead to a poorly optimized management and sustainability of bridges.

Development of lime injection grouts for the stabilisation of detached lime plasters with wall paintings in the unique Romanesque round church in Slovenia

This paper presents the design of lime grouts to stabilise wall paintings from the 13th and 14th centuries in the Romanesque church of St. Nicholas in Selo, Slovenia. Most of the paintings were executed using the secco technique on a single layer of lime plaster made of slaked lime and quartz sand, which was applied to a clay brick masonry base. The thickness of the detached pockets was generally 2 mm to 1 cm, in a few places up to 5 cm, especially in the vault area. Consolidation of detached plaster layers is an irreversible treatment to restore the adhesion between the detached plaster layers. It was therefore important that the grouts met certain criteria in terms of composition and properties in the fresh and hardened state. We developed three grouts that meet general criteria and two specific key requirements, such as low density and sufficient injectability without pre-wetting to prevent new damage and/or the plaster falling off the wall or ceiling during or after the consolidation treatment. The grouts consist of hydrated lime, fillers, polycarboxylate ether superplasticizer (PCE) and water. During the design process, various quartz fillers were tested in different proportions. The reduced density of the grout was achieved by using expanded glass granules as a partial filler substitute. The appropriate injectability of the grout was achieved through the combination of reduced water content and superplasticizer PCE.

The Safety Assessment of Chemical Grouting “Sodium Silicate-based” in Indonesian Soils

Chemical grouting is a method to improve or accelerate the solidification process on a loose soil. The implementation of improper chemical grouting may lead to affect the safety level of groundwater; thus, the technical ability and safety should be analyzed comprehensively to prevent degenerative effect on environment. Volcanic soil is targeted on this research coherent to the abundancy in Indonesia. In this study, a field scale test was conducted to validate leaching test results that were obtained in the lab and to confirm the safety of sodium silicate-based chemical grouting. In addition, the geoelectric survey was conducted to ensure the flowing of groundwater by observing resistivity of soil layer. On laboratory test result, the significance basic pH was observed, in consequence some test revealed an increase in concentration of heavy metals. The bench test was conducted in Jatinangor area’s soil as a representative of Indonesian soil to validate the laboratory result. During the bench test, the pH of ground water was monitored continuously for 5 months, where a slight increase in the pH values of ground water was observed. In addition to that, water samples were collected and analyzed in the laboratory to examine heavy metal contamination in ground water on the 18th day after the chemical grouting injection was started. However, the increased concentration was not found which indicates the pH control shall be the main control of metal leaching. As the conclusion, pH monitoring as early measurement for chemical grouting effect on groundwater is proposed to be set as standard for chemical grouting work.

Multiphase flow coupling analysis of shield synchronous grouting filling law with time-dependent viscosity

Owing to the non-visual characteristics of the shield synchronous grouting engineering, the law of grout filling in the shield tail gap remains obscure. There is a current deficiency in effective three-dimensional filling and diffusion models. Building upon a large-diameter, eight-hole shield tunneling grouting project in Hangzhou, this study aims to construct a holistic three-dimensional model of grout filling in the shield tail gap. Employing COMSOL Multiphysics and grounded on the two-phase Navier–Stokes equations, this study simulated the filling of grouting fluid in the shield tail gap. Utilizing the Brookfield DV3T rheometer, the study ascertained the time-dependent expression of grout viscosity and systematically analyzed the impacts of time-dependent grout viscosity, density, and injection pressure on the filling diffusion morphology, pressure field, velocity field, and the buoyancy experienced by the segmental lining. The results indicate that the injection pressure is positively correlated with the circumferential pressure field of the segmental lining, though the influence on the ring's total buoyancy is minimal. The rate of grout viscosity development significantly affects the overall diffusion morphology: conventional grout tends to be underfilled at the top of the shield tail gap while rapid-setting grout is more likely to be underfilled at the bottom. The grout density is positively correlated with the grout displacement speed and the total buoyancy of the segmental lining. In light of these insights, utilizing low-density, rapid-setting grout under high-pressure grouting for shield tail filling can ensure adequate filling rates while mitigating the adverse effects of segment buoyancy.

Influence law and control mechanism of overburden isolated grout injection on methane emission in the working face

Overburden isolated grout injection (OIGI) can well reduce surface subsidence, waste emission, and coal resource waste while preserving the ecological integrity of mining areas, thereby becoming the development direction of green coal mining in the future. However, its influence law and control mechanism on methane emission under coal seam mining remain unclear. In light of this, data including methane emission and surface subsidence during the mining of the 22301 working face in Tunlan Mine was collected by on-site measurements through online methane extraction monitoring systems, leveling instruments, and electronic total stations. The collected data and geological information were subject to numerical simulation and theoretical analysis to explore the methane emission law and its controlling factors after OIGI. The results demonstrate the following: (1) The total methane emission decreases by 46% after the implementation of OIGI, primarily due to reduced methane emission from the adjacent seams into the mining coal seam. (2) After OIGI, the vertical stress on the coal and rock strata in goaf rises, while the stress on the surrounding coal pillars decreases; the stress in the whole stope tends to be distributed more uniformly. (3) A relationship between the overburden stress and permeability was established, which reveals that stress plays a major role in controlling methane emission from adjacent seams into the goaf. After OIGI, the rising stress on the overburden above the goaf reduces the porosity and permeability, narrowing methane migration pathways, consequently reducing the volume of methane emission from surrounding seams into the coal seam. Stress redistribution after mining gives rise to methane rivers and low-permeability walls around the goaf, the volumes of which decrease as the grouting pressure rises. Methane rivers are where methane accumulates, and pre-drainage boreholes from adjacent seams should be directed towards these methane rivers to achieve enhanced methane extraction. The conclusions of this study provide theoretical support for efficient methane extraction under OIGI mining.

Технология инъекционной изоляции пластовых выработок угольных шахт

The basic composition of technological suspension (TS) for injection grouting of the edge part of the coal seam has been developed. The investigated water-solid TS actively show structural characteristics at different velocities of flat flow in the fracture. An increase in the TS concentration and introduction of ash-slag into the composition provides nonlinear growth of dynamic (ultimate) shear stress τ0 and is accompanied by a jump of its value in the range of water-solid ratio from 0.35 to 0.4. The schemes of grouting operations for different categories of coal seams stability have been developed, which differ in the application of spray-insulating coating, collector connection scheme and the evacuation system for the injection boreholes. Monitoring of the operating parameters with current operational assessment of the massif fracturing degree allows to control the flow movement and the TS injection pressure, reducing the solution losses while improving the quality of injection isolation.